BBK 1542 Twin 58mm Throttle Body - High Flow Power Plus Series For GM LT1 5.7L BBK is your Number One Aftermarket Performance Brand in the USA - American Designed and Built High Flow Power Plus Series Twin 58mm Throttle Body for More Modified Applications Increases Airflow to Improve Horsepower and Throttle Response Over Stock Recommended For More Modified Applications that Have Exhaust and Intake Modifications All New CNC Machined Casting Assembled with Components that Exceed OEM Standards, They Will Offer Years of Trouble Free Performance Bolt on 8-12 HP Fits Most Lt1 GM Applications, Camaro, Firebird, Corvette, Impala